The Bell X-22 is an American

V/STOL A vertical and/or short take-off and landing (V/STOL) aircraft is an airplane able to take-off or land vertically or on short runways. Vertical takeoff and landing (VTOL) aircraft are a subset of V/STOL craft that do not require runways at a ...

X-plane The X-planes are a series of experimental United States aircraft and rockets, used to test and evaluate new technologies and aerodynamic concepts. They have an X designator within the US system of aircraft designations, which denotes the exper ...

with four tilting

ducted fan In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing (VTOL) applicati ...

s. Takeoff was to selectively occur either with the

propellers A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

tilted vertically upwards, or on a short runway with the

nacelle A nacelle ( ) is a "streamlined body, sized according to what it contains", such as an engine, fuel, or equipment on an aircraft. When attached by a pylon entirely outside the airframe, it is sometimes called a pod, in which case it is attached ...

s tilted forward at approximately 45°. Additionally, the X-22 was to provide more insight into the tactical application of vertical takeoff troop transporters such as the preceding

Hiller X-18 The Hiller X-18 was an experimental cargo transport aircraft designed to be the first testbed for tiltwing and V/STOL (vertical/short takeoff and landing) technology. Development Design work started in 1955 by Stanley Hiller Jr and Hiller ...

and the X-22's successor, the Bell XV-15. Another program requirement was a true airspeed in level flight of at least 525 km/h (326 mph; 283 knots).

Design and development

In 1962, the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

announced their request for two prototype aircraft with V/STOL capability, powered by four ducted fan nacelles. Bell Helicopters already had extensive experience with

VTOL A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-wi ...

aircraft and was able to utilize an already developed test mockup. In 1964 the prototype, internally referred to by Bell as Model D2127, was ordered by the Navy and received the X-22 designation. It was unveiled at an event in Niagara Falls in May 1965. Three-bladed propellers were mounted on four wings and, synchronized through a wave-interconnection system, were connected to four

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

s which, in turn, were mounted in pairs on the rear wings. Maneuvering was achieved by tilting the propeller blades in combination with control surfaces (

elevators An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They are ...

and ailerons), which were located in the

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that sys ...

stream of the propellers.

Operational history

The maiden flight of the prototype occurred on 17 March 1966. In contrast to other tilt-rotor craft (such as the

Bell XV-3 The Bell XV-3 (Bell 200) is an American tiltrotor aircraft developed by Bell Helicopter for a joint research program between the United States Air Force and the United States Army in order to explore convertiplane technologies. The XV-3 featured ...

), transitions between hovering and horizontal flight succeeded nearly immediately. However, interest increased more towards VTOL and V/STOL properties, not the specific design of the prototype. Due to failure of a propeller control, described by test pilot Stanley Kakol as the only non-redundant component in the power chain, the prototype crashed on 8 August 1966 and technicians stripped it for components in order to make the second prototype flight capable. The

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraf ...

was still used as a

simulator A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...

for some time afterwards. The second X-22 first flew on 26 August 1967. Early that year, it was equipped with a variable flight control and stabilizer system from

Cornell Aeronautical Laboratory Calspan Corporation is a science and technology company founded in 1943 as part of the Research Laboratory of the Curtiss-Wright Airplane Division at Buffalo, New York. Calspan consists of four primary operating units: Flight Research, Transportati ...

, which improved flight performance. Although the X-22 was considered to be the best aircraft of its type at the time, the program was canceled. The required maximum speed of 525 km/h was never reached. The second prototype was moved to Cornell Aeronautical Laboratory for further testing; the last flight occurred in 1988.

Surviving aircraft

Although not on display, the only currently remaining craft, 151521, is currently stored by the Niagara Aerospace Museum, New York."Bell X-22."
''aero-web.org.'' Retrieved: 30 December 2010. According to the employees at the Museum, the craft was held onto after being debated for scrapping by the Navy.

Specifications (X-22A)

References

Citations

Bibliography

* Apostolo, Giorgio. ''The Illustrated Encyclopedia of Helicopters.'' New York: Bonanza Books, 1984. .

''

Flight International ''Flight International'' is a monthly magazine focused on aerospace. Published in the United Kingdom and founded in 1909 as "A Journal devoted to the Interests, Practice, and Progress of Aerial Locomotion and Transport", it is the world's old ...

,'' 23 March 1967, p. 445. * Markman, Steve and Bill Holder. ''Straight Up: A History of Vertical Flight''. Atglen, Pennsylvania: Schiffer Publishing, 2000. . * Rogers, Mike. ''VTOL: Military Research Aircraft.'' New York: Orion Books, 1989. .

External links

aerospaceweb.org
{{Authority control X-22 Tilting ducted fan aircraft X-22, Bell Four-engined tractor aircraft Tandem-wing aircraft Turboshaft-powered aircraft Aircraft first flown in 1966